Quote from Sabina:
For guilds that previously had guild titles, if you change the guild title name, the guild title changes immediately regardless of the number of new joining guild members.
Here are a few other facts that may help -
- For guilds that are newly created during event periods, the 5 guild founders were applied to the event and you can obtain the title.
- During the event period, you are able to obtain the guild title only when there were 5 or more characters who went through the guild registration and registration approval process.
- When you gathered 5 or more guild members during the event period, the title that was registered during the event period will be distributed to all guild members during the next maintenance.
Source
Character limit for title has increased from 7 to 10